LOS ANGELES — The flu season has gotten off to its quickest start in nearly a decade, a sign that it could be a bad year for the illness, officials said on Monday.

Health officials Monday said the primary strain circulating tends to make people sicker than other types. It is particularly hard on the elderly.

Dr. Thomas Frieden, the director of the federal Centers for Disease Control and Prevention, urged people to get a flu shot to minimize the impact of the deadly disease’s spread.

Speaking to publicize National Influenza Vaccination Week, Frieden said a flu shot was the best tool available to stop the spread of the disease, along with covering your mouth when coughing and washing your hands.

“This is the earliest regular flu season we’ve seen in nearly a decade,” Frieden said in a conference call with reporters. “That suggests this could be a bad flu year.”

An uptick like this usually doesn’t happen until after Christmas.

Flu-related hospitalizations are also rising earlier than usual, and there have already been two deaths in children.

Based on early testing, Frieden said the number of suspected flu cases has jumped in five Southern states: Alabama, Louisiana, Mississippi, Tennessee and Texas.

The dominant flu type is the same as the one associated with the flu season of 2003-2004, when the outbreak was bad, he said.

In Washington, flu-like illnesses have increased in the past month but remain well below epidemic levels, health officials said, and no deaths have been reported.

Typically, flu activity peaks in Washington in January or February and occasionally as late as April, said Donn Moyer, spokesman for the Washington State Department of Health.

“Get a flu shot,” Moyer said. “It’s good for a year; protect yourself.”

The flu is caused by different strains, and part of the test for scientists is trying to mix a vaccine that includes the strains most likely to be dominant in any given season.

The current vaccine, prepared in advance, seems well-matched for the strains working their way through the population, Frieden said.

It’s not clear why the flu is showing up so early.

The last time the season started this early, it proved to be one of the most lethal seasons in the past 35 years, with more than 48,000 deaths. The dominant type of flu then was the same one seen this year.

One key difference between then and now: In 2003-04, the vaccine was poorly matched to the predominant flu strain.

Also, there’s more vaccine now, and vaccination rates have risen for the general public and for key groups such as pregnant women and health-care workers.

An estimated 112 million Americans have been vaccinated so far, the CDC said. Flu vaccinations are recommended for everyone 6 months or older.

On average, about 24,000 Americans die each flu season, according to the CDC.

Flu usually peaks in midwinter.

Its symptoms can include fever, cough, runny nose, head and body aches and fatigue.

Some people also suffer vomiting and diarrhea, and some develop pneumonia or other severe complications.

A strain of swine flu that hit in 2009 caused a wave of cases that spring and then again in early fall. But that was considered a unique type of flu, distinct from the conventional strains that circulate every year.

With the holiday season in mind, Frieden urged people be careful.

“Spread good cheer and give presents,” he said. But “don’t share infections and spread the flu.”

Seattle Times health reporter Carol Ostrom contributed to this report.